1. Ch.11-1
Mendel
genetics

2. POINT > Define heredity and genetics
POINT > Introduce Mendel
POINT > Describe Mendel’s approach to his experiments
POINT > Relate Mendel’s experiments to current knowledge

3. POINT > Define heredity and genetics
Heredity is the transfer of characteristics from parent to offspring Genetics is the study of heredity

4. POINT > Define heredity and genetics
Thinking into the 1800’s: Traits BLENDED between parents

5. Gregor Mendel (1822 – 1884) POINT > Introduce Mendel Austrian Monk
High school teacher
Responsible for the monastery garden
Used pea plants to study heredity

6. POINT > Describe Mendel’s approach to his experiments
Why were pea plants so useful in these expriments?
1. Easy to grow and grow quickly (reproduction ~ 90 days)
2. Lots of offspring (good for statistical analysis)
3. Easy to control plant mating (self-pollinating)
4. Easily viewed, dichotomous traits!

7. WB CHECK: Which is not a reason pea plants were useful to Mendel?
a) grow quickly
b) self pollinate
c) require very little water
d) have traits that are easy to see
e) easy to control mating
Where did Mendel do his experiments?

8. POINT > Describe Mendel’s approach to his experiments
Pollen located in the
anthers of the stamen
Peas have both male (pollen) & female (ovule/egg) reproductive parts
Peas often self-pollinate, which results in purebred offspring: Genetically identical to parents
Ovule located in the
ovary of the pistil

9. POINT > Describe Mendel’s approach to his experiments
Mendel removed the stamen before self-pollination
This allowed Mendel to control which plants crossed with each other (no self-pollination)

10. POINT > Describe Mendel’s approach to his experiments
Mendel manually pollinated each plant
So any variations were due to his experiments

11. POINT > Describe Mendel’s approach to his experiments
Seed Shape
Flower Color
A trait is a specific characteristic of an individual
Mendel studied seven observable traits in peas
Seed Color
Pod Color
Plant Height

12. POINT > Describe Mendel’s approach to his experiments
Mendel first crossed purebreds that had trait differences
Green
Seed
Yellow
Seed P
(Parental) ? F1
(First Generation)

13. POINT > Describe Mendel’s approach to his experiments
Hybrids are offspring that result from crosses between parents with different traits

14. POINT > Describe Mendel’s approach to his experiments
Mendel first crossed purebreds that had trait differences P
(Parental)
All offspring were yellow F1
(First Generation)
This happened with all of the traits he tested

15. POINT > Describe Mendel’s approach to his experiments
Mendel then allowed F1 plants to self-pollinate F1
(First Generation) ? F2
(Second Generation)

16. POINT > Describe Mendel’s approach to his experiments
Mendel then allowed F1 plants to self-pollinate F1
(First Generation) F2
(Second Generation)

17. POINT > Describe Mendel’s approach to his experiments
Mendel then allowed F1 plants to self-pollinate
75% Yellow, 25% Green
All the traits he tested had a 3:1 ratio in the F2 F2
(Second Generation)

18. WB CHECK:
When Mendel crossed purebred plants in the P generation, what percentage of the F1 offspring had green seeds?
When Mendel crossed F1 plants, what percentage of the F2 offspring had green seeds?

19. POINT > Describe Mendel’s experiments
Another example: cross a purebred purple flower plant with a purebred white flower plant

20. POINT > Describe Mendel’s experiments
When Mendel did this cross, purple x white, all of the offspring had purple flowers.

21. POINT > Describe Mendel’s experiments
Mendel then let the F1 generation self-pollinate (F1 x F1)
Remember, all these plants had purple flowers

22. POINT > Describe Mendel’s experiments
25% of the F2 generation were white!
The same was true of the other traits 75% -25%

23. POINT > Relate Mendel’s experiments to current knowledge
Genes are factors passed from one generation to the next that determine an individual’s characteristics ex. pea color, plant height, etc

24. POINT > Relate Mendel’s experiments to current knowledge
Alleles are different forms of a gene that occur at the same location on a chromosome
One allele is inherited from each parent (two total)
Often, only one allele can be expressed (Principle of Dominance)

25. POINT > Relate Mendel’s experiments to current knowledge
A dominant allele is always expressed if it is present ex. Both alleles are dominant ex. Alleles are different

26. POINT > Relate Mendel’s experiments to current knowledge
A recessive allele is only expressed when the dominant allele is not present (ex. green seed allele)

27. POINT > Relate Mendel’s experiments to current knowledge
Segregation is the separation of alleles during gamete formation
Meiosis!! When homologous chromosomes separate, the two sets of alleles are segregated

28. POINT > Relate Mendel’s experiments to current knowledge
Mendel deduced that factors (genes) came in pairs, which were segregated during reproduction
Mendel’s work was published in 1866, but went unnoticed until many years after his death
The discovery of his work led to the basic principles of genetics

29. Next: We will apply Mendel’s principles… Read 11. 1 S. A
Next: We will apply Mendel’s principles… Read 11.1 S.A. #1-2 page 312 Exam Prep